Disabeling of the translation selector
I'm guessing you're adding vertices by Ctrl-clicking.



This button, or CtrlSpacebar toggles the visibility of the manipulator.

Using one of the shortcuts - (G,R,S) for translation, rotation, or scale, dismisses the manipulator, even if it was visible. 

In an orthogonal view, using E to extrude, (rather than place,) new vertices, allows you to move them about in screen space, without having to go to a separate operation.